libtommath/etc/2kprime.c

/* Makes safe primes of a 2k nature */
#include <tommath.h>
#include <time.h>

static int sizes[] = {256, 512, 768, 1024, 1536, 2048, 3072, 4096};

int main(void)
{
   char buf[2000];
   int x, y;
   mp_int q, p;
   FILE *out;
   clock_t t1;
   mp_digit z;

   mp_init_multi(&q, &p, NULL);

   out = fopen("2kprime.1", "w");
   for (x = 0; x < (int)(sizeof(sizes) / sizeof(sizes[0])); x++) {
top:
      mp_2expt(&q, sizes[x]);
      mp_add_d(&q, 3, &q);
      z = -3;

      t1 = clock();
      for (;;) {
         mp_sub_d(&q, 4, &q);
         z += 4;

         if (z > MP_MASK) {
            printf("No primes of size %d found\n", sizes[x]);
            break;
         }

         if ((clock() - t1) > CLOCKS_PER_SEC) {
            printf(".");
            fflush(stdout);
//            sleep((clock() - t1 + CLOCKS_PER_SEC/2)/CLOCKS_PER_SEC);
            t1 = clock();
         }

         /* quick test on q */
         mp_prime_is_prime(&q, 1, &y);
         if (y == 0) {
            continue;
         }

         /* find (q-1)/2 */
         mp_sub_d(&q, 1, &p);
         mp_div_2(&p, &p);
         mp_prime_is_prime(&p, 3, &y);
         if (y == 0) {
            continue;
         }

         /* test on q */
         mp_prime_is_prime(&q, 3, &y);
         if (y == 0) {
            continue;
         }

         break;
      }

      if (y == 0) {
         ++sizes[x];
         goto top;
      }

      mp_toradix(&q, buf, 10);
      printf("\n\n%d-bits (k = %lu) = %s\n", sizes[x], z, buf);
      fprintf(out, "%d-bits (k = %lu) = %s\n", sizes[x], z, buf);
      fflush(out);
   }
   fclose(out);

   return 0;
}

/* ref:         $Format:%D$ */
/* git commit:  $Format:%H$ */
/* commit time: $Format:%ai$ */